Pointers to node groups?
Randomizing Texture Locations

Here are 3 node tree setups that allow one texture to be randomly placed on multiple objects:  

(NOTE: If you can't see the node tree graphics easily here, you can download them to see them in much higher resolution)  

Node Tree #1:

  


NOTE: In the Vector Curves node here, see how the curve has been changed from it's default straight line to a curve and how the X button is selected above that on the left? Well, in order for the randomization to be most comprehensive, you need to similarly change the curve for Y and Z -- just click on each and adjust it's curve.  


Node Tree #2:



Node Tree #3:

  


NOTE: The node called "Object Variation" is a node group. To expand the group so you can see and/or edit all the nodes in it, select it and press TAB (and TAB again to collapse the group). Here are the nodes in the group:  




Points to Note


You probably will want to use a seamless tileable wood texture so you don't have seams showing on occasion.  
You can use either Photoshop or GIMP to create your own seamless texture:  


In GIMP:  Filters -> Map -> Make Seamless
NOTE: GIMP's "Make Seamless" works very well if the texture is very vague, like sand on the beach, but it doesn't work well at all if the texture is very well defined, like zebra stripes.
In Photoshop  



And to give credit where due:  


The 1st node tree came from Benjamin Dod on BlenderArtists.org  and here is his blend file 
The 2nd node tree came from User2554615 here on StackExchange and here is the blend file  
The 3rd node tree came from Rich33584 also on BlenderArtists.org  and here is his blend file